Rain at the jubilee weekend. The next few days are expected to be relentlessly wet and windy. Photograph: Veronika Lukasova/ZUMA Press/Corbis

An unseasonable Atlantic storm is set to batter the UK, with gale-force winds and heavy rain expected in many parts of the country on Thursday, continuing and spreading into Friday.

The Met Office issued a severe weather warning for south-west England from early Thursday afternoon, with an amber warning issued for Devon, Cornwall and the Isles of Scilly.

Gusts of up to 70mph are expected to hit coastal areas by mid-afternoon, risking damaging trees and dislodging roof tiles. Travel may also be disrupted and with many children on half term this week, family plans and holidays are likely to be dampened.

The forecaster Mark Seltzer said: "Strong winds, possibly up to gale force, are expected from the afternoon onwards in south-west England, particularly Devon and Cornwall."

The bad weather will spread across the country with Wales also expected to be whipped by strong winds. "On Friday the warning is extended to include south Wales and many parts of southern England as well as the south-west, again with a risk of gales. The public should be careful when they are outside, and there is a danger of damage to trees," he said.

But as Friday progresses winds are expected to ease gradually from the south-west during the day.

Brendan Jones, a senior forecaster with MeteoGroup, said the sort of Atlantic storm set to hit Britain was out of character for June, and was more common in the autumn and winter months. "Winds will increase this afternoon in Devon and Cornwall and there could be gusts of 60 to 65mph or even 70mph on exposed coasts and headlands," he said. "Through tonight and Friday, the centre of the storm will move slowly north east, touching areas as far away as north Wales and exiting Britain as far north as Northumberland."

The next few days look set to be relentlessly wet and windy, he added, with parts of inland England experiencing winds of more than 50mph. "There will also be a lot of rain in the next 48 hours," he said.